Electric wave transmission system



Oct. 25, 1932. A. G. JEN SEN ,88

' ELECTRIC WAVE TRANSMISSION SYSTEM Original Filed Dec. 4, 1924 ATTOPNE) Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE AXEL G.JENSEN, OF RED BANK, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY,INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTRICWAVE TRANSMISSION SYSTEM Original application filed December 4, 1924,Serial No. 753,813, now Patent 1,722,094, dated July 23, 1929. Dividedand this application filed April 24, 1929. Serial No. 357,846.

This application is a division of application Serial No. 753,813, filedDecember 4,1924: patented July 23, 1929, No. 1,722,094.

This invention relates to electric wave translation systems and moreparticularly to space discharge tube systems wherein the production ofundesired oscillations is prevented.

It is now well known that, in a space discharge tube system,oscillations will be generated when the input and outputcircuits of thetube contain reactances of the proper kind and of the proper value.These oscillations are generated by virtue of the amplifying action ofthe tube, and by virtue of the coupling afi'orded between these circuitsbythe inherent capacity between the tube electrodes and the externalleads associated therewith. On the basis of this knowledge, systems havebeen devised in which the tendency to generate undesired oscillations isreduced, by providing a balancing capacity for neutralizing the tubeelectrode capacity.

It has been found, however, that when tubes of great amplifying powerare employed, or when a large number of tubes are placed in tandem, asystem arranged for capacity neutralization may provide a new path inwhich parasitic oscillations may be generated. The invention to behereinafter described provides a solution of this problem.

An object of the invention is to prevent the generation of parasiticoscillations in wave translation systems, particularly those includingspace discharge devices.

Another object is to so alter the reactance of wave translation systemsor space discharge tube systems as to avoid a condition favorable to thegeneration of oscillations.

A further object is to prevent the flow of oscillatory waves throughspecified paths in a space discharge tube system.

An additional object is to prevent the flow of undesired oscillatorywaves by impeding them.

A feature of the invention is a space discharge tube system providedwith impedance for preventing the flow of oscillatory currents in thesystem.

Another feature is a space discharge tube sistances therein.

system provided with paths including resistance, whereby an oscillatorycondition of the system is avoided.

The present invention involves certain principles which are applied tosystems of space discharge'tubcs to obtain the objects above enumeratedand others. In order to prevent undesired oscillations in systems ofspace discharge tubes, the circuits included therein may be so designedthat paths, wherein oscillatory currentstend to flow, will con tain anelement or elements for impeding oscillations. For example, theimpedance element may be a resistance. In the specific form of theinvention shown in the drawing, a space discharge amplifier has itsinput circuit balanced by means of a capacity arranged to neutralize theeiiect of interelectrode capacity of the space discharge tube. Inarrangements of this kind, "heretofore known, parallel paths betweenthetube input and output circuits are provided wherein oscillations maybe generated. The system shown in the drawing provides means forpreventing oscillations in these paths by providing, for example,non-inductive re- One of these resistances is connected between the gridand the filament of the space discharge tube and the other is connectedbetween the filament and the neutralizing capacity. The resistances formtwo arms of abalanced circuit which has the circuit configuration orform of a VVheatstone bridge and which has as its other two arms theplate-grid capacity of the tube and the neutralizing capacity.

The output diagonal of the circuit includes the plate filament spacepath. The input diagonal includes a timed circuit, and this tunedcircuit and the arms are mutually exclusive, so that the balance luponwhi ch depends the neutralization of the coupling effect of thegrid-plate capacity is independent of the potential gradient along thetuning capacity, whereas were port-ions of that capacity included. inarms of the circuit the balance condition would depend on themaintaining of a given ratio between those portions.

The invention is described in detailin the following specification readin connection with the attached drawing.

The single figure of the drawing represents schematically a spacedischarge tube system embodying a form of the invention.

In the drawing, a space discharge tube 10 having anode, cathode andcontrol electrodes 11, 12 and 13, respectively, is arranged in a circuitincluding resistance elements 26 and 26 and a capacity element 15 forpreventing oscillations in the system. The space dis charge tube 10 hasan input circuit connected to its control electrode and cathode whichincludes a resonant circuit 17 comprising a condenser 18 and inductance19, a polarizing battery 20, and resistances 26 and 26. Resonant circuit17 may be tuned by adjusting condenser 18. The ends of the winding ofcoil 19 are connected to the cathode by a path including the gridpolarizing battery 20and resistances 26 and 26. One terminal of thewinding of coil 19 is connected to the control electrode 13, whereas itsopposite terminal is connected to the anode 11 by a path includingcondenser 15. The output circuit of tube 10 extends from anode 11,through an inductance 24 and a source of space current 23 to itscathode. The condenser 25, shown in dotted lines, represents theinherent capacity between the anode 11 and control electrode 13 of tube10 plus the capacity of the leads connected to these electrodes.

Waves to be amplified may be'supplied to the input circuit through thewinding of coil 19 which also represents a transformer, a wavecollecting conductor such as a loop antenna, or similar device.Amplified waves may be transmitted to any suitable apparatus externalto. the system coupling by suitable means associated with the coil 24.

In amplifying systems as ordinarily arranged the midpoint of coil 19 isconnected to cathode 12, and the capacity 25, shown in dotted lines, byprovid ng a feed back path from the anode to the control electrode ofthe tube, permits the transfer of waves from its output circuit to itsinput circuit which may cause the production of undesired oscillations.With such. systems'in an effort to neutralize the effect of capacity 25,the anode 11 is connected to the cathode 12 by a path including thebalancing condenser 15. This path is in parallel with that including thecapacity 25. Varying currents flow inthe two parallel paths through therespective halves of coil 19 in such manner as to induce electromotiveforces therein which are theoretically equal and opposite, so that nopotential variations are impressed upon control electrode 13.

In practice, it has been found that in such systems the balancingcapacity 15 in parallel with the tube capacity 25 constitutes new pathsin which oscillations may be generated,

5 especially, when tubes of high amplifying power are employed unlessadditional means is produced to prevent their occurrence. This fact willbe understood when I consider that the input circuit of tube 10 in suchsystems contains an inductance, represented by the difference betweenthe self-inductance of coil 19 and the mutual inductance between its twohalves, and the output circuit contains the inductance 24. It is wellknown that a space discharge tube system, including inductivereactancesin both the input and output circuits and capacity couplingbetween them, will generate oscillations at certain frequencies forwhich these reactances cooperate to constitute a resonant circuit.

The system shown in the. drawing prevents production of suchoscillations. This system is similar to the prior art system'reierred toabove, but it has not the above mentioned connection from the cathode tothe midpoint of coil 19, and it has two resistances 26 and 26 connectedrespectively between the cathode of tube 10 and the two outer terminalsof the winding of coil 19. These resist'ances are included in theparallel paths between the anode and cathode and are of such value as togreatly impede the flow of oscillatory waves and, if desired, to causethe tube to operate as a distorting device for the impressed waves,whereby detection or denser 15 and resistance 26' on the other. So faras concerns the energy fed back tubes having equi-potential cathodes, i.e., J1;

cathodes heated by induction or heat radiation such as described in thepatent to Nicolson No. 1,459,412, granted June 19, 1923, but thisstatement should not be taken to indicate that the utility of theinvention is in any manner limited to a particular type of tube.

Although, for the purpose of explaining the invention, it has beendescribed in connection with a certain specific circuit arrangement, theprinciples involved are capableof general application to a range ofequivalents which will readily occur to persons skilled in the art, andconsequently this invention is to be limited only as indicated by thescope of the appended claims.

What is claimed is:

1. A circuit of Wheatstone bridge configuration comprising an electricspace discharge device having therein an anode-catln ode path and acontrol element anode path, said circuit having four arms and twodiagonals with one of said paths in an arm and the other in a diagonaland with an impedance element external to said device included in eachof said other arms, and a tuning circuit included in one of saiddiagonals, said tuning circuit and said arms bein mutually exclusive,and two of said impedance elements being resistances.

2. A circuit of l/Vheatstone bridge form comprising an electric spacedischarge device having therein an anode-cathode path and a controlelement anode path, said circuit having four non-inductive arms and twodiagonals with one of said paths in an arm and the other in a diagonaland uiti an impedance element external to said device included in eachof said other arms, and a tuning circuit included in one of saiddiagonals, said tuning circuit and said arms being mutually exclusive,and two of said impedance elements being resistances.

3. A Wheatstone bridge form of circuit comprising an electric spacedischarge device having therein an anode, a cathode, control element andan anode-cathode path and a control element-anode path, and having itscontrol element-anode capacity balanced to prevent singing, said circuitcomprising four arms and an input diagonal and an output diagonal, withsaid control element-anode path in an arm and said anode-cathode path insaid output diagonal, a tuning circuit included in said input diagonal,said tuning circuit including a variable tuning capacity, said tuningcircuit and said arms being mutually exclusive, and a noninductiveresistor included in each of the two of said arms that are connected tosaid cathode, whereby singing through arms of the circuit parallel pathsis prevented and balance of the circuit with respect to action of wavesfrom the output diagonal upon the input diagonal is independent of thepotential gradient along the tuning capacity.

4.. A space discharge tube system having a. three electroue tube, atuning circuit comprising an inductance element and a capacity,electrodes of said. tube being connected to electrically separate pointsin said tuning circuit, means to balance the capacity between two ofsaid. electrodes and additional means cooperating with said balancingmeans to suppress parasitic oscillations in the system due to saidinter-electrode capacity in cooperation with said balancing means, saidadditional means comprising non-inductive resistors in shunt to saidtuning circuit and connecting the cathode of said tube to said tuningcircuit only at the ends of said inductance element.

5. An audion amplifier the impedance network of which is arranged in theform of an alternating current VVheatstone bridge having four balancingarms one of which is the grid-plate capacity of the audion tube, one ofwhich is a capacity connected between the plate of: said tube and oneterminal of the input circuit, one of which is a resistive impedanceconnected between the cathode of said tube and said terminal of theinput circuit, and one of which is a resistive impedance connectedbetween the grid and cathode of said tube.

6. In combination, a three-electrode audion tube having an inherentgrid-plate capacity, a resistance connected between the grid and cathodeof said tube, a resistance and a capacity connected in series in theplate circuit of said tube, and an input circuit one terminal of whichis connected to the grid of said tube and the other terminal of which isconnected to an intermediate point in the plate circuit impedance ofsaid tube.

7. The combination with a three-electrode thermionic device havinganode, cathode and grid electrodes and an input circuit, a resistanceconnected between the grid and cathode of said thermionic device, aconnection comprising a second resistance and a capacity connected inseries between the cathode and anode of said thermionic device and aninput element connected between the grid and the junction of said seriesconnected resistance and capacity.

8. An electrical amplifier circuit comprising, in combination, a vacuumtube amplifying device, an output circuit for the amplifier stage, aninput circuit for said stage, and impedance elements forming analternating current /Vheatstone bridge of which said output and inputcircuits form conjugate arms, two balancing arms of said bridgerespectively comprising capacity between anode and control electrode ofsaid tube and a resistance between cathode and control electrode of saidtube, and the two remaining balancing arms being constituted by aresistance and a. capacity connected in series between cathode and anodeof said tube.

9. An audion amplifier stage wherein an audion and a plurality ofimpedances form an alternating current lVheatstone bridge network havingas conjugate arms thereof the input circuit and the output circuit ofsaid stage, characterized by the fact that the two bridge armsterminating at the plate terminal of the audion are capacitive, and theimpedances of the two bridge arms terminating at the filament terminalof the audion are resistive.

In witness whereof, I hereunto subscribe my name this 8th day of April,1929.

AXEL G. JENSEN.

